BGP redist into ospf

Guys we have a environemnt in which we are running ospf on your LAN side and BGP on WAN.....ospf is being redistributed into bgp and bgp is redistributed into ospf.....now we are getting default route and some specific routes from our provider.......i have done the following

router ospf 1

redistribute bgp subnets

will it work??? or do we have to add default-information command as well...........if yes why?? thanks

secondly AS-path prepend and MED.......both do the same thing why would we use MED instead of as path prepend and same as other way around